I use K9 Advantix II for my girls (approx. 3yrs, 6lbs) but use half of the tube on each. It states (as many of them do) that you can use on dogs "7 weeks and older", and most of the products lowest dosing is "up to 10lbs". That said, using 1/2 the tube would work for Hailey - if you feel comfortable doing so
